淬（cuì）火，金属和玻璃的一种热处理工艺。把合金制品或玻璃加热到一定温度，随即在含有矿物质的水、油或空气中急速冷却，一般用以提高合金的硬度和强度。

淬火可增强钢铁和合金的强度和硬度。急速冷却的速率也会影响物质表面硬度和心部硬度。淬火后物质会变脆，所以通常会再进行回火处理，目的是降低物质的脆度。螺丝、齿轮、转动轴、金属块等物品常使用淬火处理。

淬火常用于碳钢

加热后使用大量的清水急速降温，可得到高硬度的钢材

In materials science, quenching is the rapid cooling of a workpiece to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such asphase transformations, from occurring. It does this by reducing the window of time during which these undesired reactions are both thermodynamically favorable, and kinetically accessible; For instance, quenching can reduce the crystal grain size of both metallic and plastic materials, increasing their hardness.